Thermostatically controlled heaters for aquariums have been proposed and built in recent years utilizing many different designs. Many of the various designs have been created in apparent attempts to solve the problem of overheating and the danger of electrical shock which are always present with the use of such devices in water filled aquariums. U.S. Pat. No. 2,736,791 to Krah et al shows an electric water heater having an insulated Nichrome resistance wire 34 wound in a coil and located in a heat resistant tube 1. Willinger U.S. Pat. No. 3,107,289 shows an aquarium heater having a heating element 19 comprising a grooved cylindrical body 36 of ceramic which supports heating coils 37, all of which fit in a heat resistant glass tube 11. Arak U.S. Pat. No. 3,564,589 shows an aquarium heater utilizing a tube 40 of heat resistant glass having a Nichrome heating element 28 mounted on a heat insulating block 63.
Volker U.S. Pat. No. 3,617,701 shows an immersible electric heating element having a quartz tube 12 in which is located an electric heating element comprising a resistance wire wound helically about a ceramic core. Bleiweis U.S. Pat. No. 3,731,058 shows an aquarium heater which, according to its specification, is designed to eliminate localized hot spots which can damage the aquarium heater housing. The heater has an electrical coil 26 located inside a heat resistant and transparent housing tube 11. The heating coil is helically enwrapped about a support member 30 with the helical turns seated in slots 33 of the support member. To prevent hot spots, the heating coil is provided with two mutually crossing helical portions over the entire extent thereof to provide a uniform heating of the heater housing tube 11.
U.S. Pat. Nos. 3,895,217 and 4,021,643 to Hall et al shows safety heaters for aquariums utilizing a heater element immersed in a heat conducting, thermally expansible liquid. U.S. Pat. No. 4,007,371 to Njos et al shows an immersion heater having a U-shaped heating rod 36 in direct contact with the water being heated.
An object of this invention is an electrical heater for an aquarium which is relatively simple and inexpensive to manufacture yet is resistant to overheating and free from the danger of electrical shock.
Another object of this invention is an aquarium heater having a plastic housing and a heater arrangement which will not develop hot spots in the plastic housing walls.
Another object of this invention is an aquarium heater which uses a low wattage insulated resistance rope heater.
Another object of this invention is a floating heater for an aquarium which is self righting if overturned.
Other objects may be found in the following specification, claims and drawings.